Pesticides have been used for thousands of years. The types of substances have changed dramatically through the years. Inorganic substances such as sulfur, arsenic, and lead were used prior to World War II.

Synthetic compound development prospered after WWII and included the infamous DDT (dichlorodiphenyltrichloroethane). This organochlorine compound was top choice for its ability to kill a wide range of pests inexpensively. DDT was also water soluble and didn’t appear to pose significant risks to mammals.

DDT’s future took a downturn in the early 1960s when research suggested it was in fact dangerous. Non-target plants and animals were harmed and pesticide residue started showing up in unconventional places. Liberal applications also made some pests genetically resistant, requiring higher doses to remain effective.

Research also suggested that long term exposure to DDT may be involved in some cancers, reproductive abnormalities, and other harmful side effects. Rachel Carson’s 1962 book “Silent Spring” suggested DDT use was leading to the near extinction of some bird species because of eggshell thinning in bird eggs.

The U.S. Environmental Protection Agency pulled DDT’s registration in 1972, effectively pulling it off the market. Other organochlorine compounds were eventually banned by the EPA and replaced with other types of compounds, including:

Organophosphates – a group of insecticides that alter nerve responses. Residential use of organophosphates are banned in the United States, but are still used in agricultural settings. Diazinon was used in many lawn and garden spray products until it was phased out in 2003.

Carbamates – insecticides made from carbamic acid that work in much the same way as organophosphates, but are considered less toxic. They are used in sprays or baits to kill cockroaches, ants, and fleas.

Pyrethroids/Pyrethrins– used widely in and around households (i.e. on pets or in mosquito control) and in agriculture. Pyrethrins are derived from chrysanthemum flowers. Pyrethroids are synthetic chemicals derived from pyrethrins and are less likely to break down when exposed to light.

Biopesticides – derived from natural materials as animals, plants, bacteria, and certain minerals. These are inherently less toxic than other forms of pesticides. Biopesticides are also more specific to the type of pest it controls. They decompose quickly and are often used in integrated pest management (IPM) systems.

Today, IPM is a popular approach to pest control that uses crop production methods that uses beneficial predators or parasites that attack pests. Pesticide applications are also timed to coincide with the most susceptible period of a pest’s life cycle. IPM is used to reduce, not replace, the use of overall pesticides.

The use of pesticides leaves residue on plants and food. The EPA establishes maximum safe levels for each food. There has been much debate about pesticide residue and the long term health and environment impacts. Pesticides are considered necessary to keep crop production in line with demand, while keeping prices affordable for consumers.

Tune in next week when we explore those long term health and environmental impacts.